I said to him, "Shall I tell you where the men are who believe most in themselves?
For I can tell you. I know of men who believe in themselves more
colossally than Napoleon or Caesar. I know where flames the fixed
star of certainty and success. I can guide you to the thrones of
the Super-men. The men who really believe in themselves are all in
lunatic asylums." He said mildly that there were a good many men after
all who believed in themselves and who were not in lunatic asylums.
"Yes, there are," I retorted, "and you of all men ought to know them.
That drunken poet from whom you would not take a dreary tragedy,
he believed in himself. That elderly minister with an epic from
whom you were hiding in a back room, he believed in himself.
If you consulted your business experience instead of your ugly
individualistic philosophy, you would know that believing in himself
is one of the commonest signs of a rotter. Actors who can't
act believe in themselves; and debtors who won't pay. It would
be much truer to say that a man will certainly fail, because he
believes in himself. Complete self-confidence is not merely a sin;
complete self-confidence is a weakness.
GK Chesterton - Orthodoxy